1. Field of the Invention
This invention relates to novel compounds useful in photography and in particular to new ammonium mercaptoalkane-sulfonate salts useful as fixing agents for developed silver halide photographic elements, and to their preparation. The invention also concerns novel aqueous fixing solutions containing such compounds, and a novel method of fixing developed silver halide photographic elements.
2. Description of the Prior Art
After an exposed photographic silver halide emulsion is developed and a silver image is produced in the areas of exposure, the silver halide in the unexposed areas is conventionally removed as a soluble silver compound with hypo or other fixing solution if a permanent silver image is desired. It is also possible to fix or stabilize the unexposed and/or undeveloped silver halide by reaction with a compound which forms a silver salt or complex that is colorless or relatively light in color and resistant to print out. A large number of agents form soluble complexes with silver which are sufficiently stable to allow them to function as fixing agents for photographic emulsions. However, in addition to dissolving the silver halides, the fixing agent must form complexes that are stable upon dilution so that insoluble salts will not precipitate during the early stages of washing. Also, the fixing agent should not attack the gelatin of the emulsion or the developed silver to an extent detrimental to the image. Practical considerations in a search for organic compounds suitable as silver complexing agents are:
1. THAT THEY EXHIBIT A FAST RATE OF FILM CLEARING;
2. THAT THEY ARE READILY PREPARABLE BY A SIMPLE PROCESS; AND
3. THAT THEY ARE REASONABLY STABLE TOWARD AIR.
Accordingly, it is an object of this invention to provide a new class of silver complexing agents.
It is another object to develop a simple 1-step process for the preparation of silver complexing agents.
Still another object is to provide novel aqueous fixing solutions containing the novel agents, and a novel method of fixing developed photographic film therewith, which exhibit a faster rate of film clearing than other agents.
Another object is to provide silver complexing agents as silver halide solvents, which are resistant to air oxidation.
Additional objects and advantages of the present invention will become apparent from a consideration of the following specification and appended claims.